The present invention relates to a method and apparatus for early fault detection in a centrifugal pump that is equipped with a balancing device. The balancing device has an axial gap and optionally one or more radial gaps through which a balancing flow is conducted. Further, a spring element is provided, which acts upon the balancing device to hold open (i.e., oppose complete closure of) the axial gap.
For early fault detection in centrifugal pumps, sensors have thus far been used, which detect any abnormal vibrations, temperature rises, noises or other measurable quantities and forward this data to a monitoring unit. For this purpose, a plurality of such sensors has been arranged on the outside of the pump housing. Thus, there was no direct connection with the site of the fault's source. The signals acquired by the sensors were not always clear and unambiguous, such that false messages could not be excluded. In particular, there was a risk that such messages came late, i.e., after damage had already occurred.
A significant fault in the interior of a centrifugal pump occurs if bearings are worn or if a balancing device no longer works sufficiently. Such a fault can come about gradually. It may initially not produce any symptoms detectable on the outside of the centrifugal pump and may manifest itself only after significant damage has occurred and possibly only after the centrifugal pump has failed.
It is possible to detect axial forces with the aid of an axially contacting sensor, i.e., a so-called a load cell. For structural reasons, however, such a load cell cannot be used continuously over a long period of time.